The design of advanced composites often seeks to balance stiffness and ductility, a challenging compromise in material science. In this study, we explore co-continuous UHMWPE (Ultra-High Molecular Weight Polyethylene)/Aluminium composites, taking advantage of the exceptional ductility of UHMWPE with the rigidity and plastic deformation potential of metallic reinforcements[1].
A key innovation in this work is the use of rapid sintering via induction heating to address processing challenges. The "melting explosion" phenomenon in nascent UHMWPE powders allows ultra-fast sintering, enabling the formation of a polymer/metal co-continuous composite with controlled microstructures[2,3]. Aluminium architected materials with different geometries were fabricated through a hybrid process combining additive manufacturing and investment casting, and then filled with UHMWPE powders[4]. The metallic phase not only reinforces the composite but also acts as a heating vector, ensuring efficient sintering.
To enhance understanding of the sintering process, numerical modelling using ANSYS was employed[5]. Based on the experimental heating profile of the metal and the thermal properties of the polymer, the model predicts polymer behavior during heating. After sintering, X-ray tomography confirmed the structural integrity of the metallic network, highlighting minimal plastic deformation and low porosity levels.
Mechanical behavior under compression was then investigated. Results have revealed that the geometry of the metallic architecture significantly impacts composite properties. These different geometries allow tuning of stiffness and ductility, offering versatile performance characteristics.
This work demonstrates the potential of co-continuous composites for applications requiring tailored mechanical properties and establishes a framework for integrating experimental and computational approaches to composite design.

During the past decade, numerous studies have been focused on understanding the glass transition (Tg) phenomena in thin polymer films and the interplay between the substrate and free surface effects [1]. The confinement impact on macromolecular mobility has been shown to depend on the type of confinement: free standing films, supported thin films, thin films capped between two surfaces [2]. Compared to those systems, layer-multiplying co-extrusion allows processing films containing thousands of alternating layers, with individual thicknesses that may reach the nanoscale [3], and displaying thin layers symmetrically confined between the walls of another confining polymer. In such systems, the existence of an interdiffusion zone, namely an interphase, at the interface between layers of two immiscible polymers must be considered. The interphase thickness may vary depending on the interactions between the two polymers, and its impact on the Tg variations and the molecular mobility of the amorphous phase is still an open question.
In this work, we study different coextruded multilayered films composed of two polymers with various compatibilities: from incompatible, like Polystyrene (PS) and Polymethyl Methacrylate (PMMA), to highly compatible, like Polycarbonate (PC) and Polyethylene Terephthalate glycol (PETg), with theoretical individual layer thicknesses down to 3 nm. The combination of different characterization techniques (modulated temperature scanning calorimetry (MT-DSC), dynamic mechanical thermal analysis (DMTA), dielectric relaxation spectroscopy (DRS)) is used to investigate the influence of the layer thickness reduction on the dynamic glass transition and the molecular mobility.

Carbon nanotubes (CNTs) were incorporated into poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends, with an epoxy compound (ADR) acting as a compatibilizer, to form the blend-based nanocomposites. Scanning electron microscopy results showed a sea-island morphology in PLA/TPU (7:3) blend and a co-continuous morphology in PLA/TPU (5:5) blend. The addition of ADR improved the compatibility between PLA and TPU; the added CNTs were mainly distributed in the TPU phase. Differential scanning calorimetry results revealed that the inclusion of ADR inhibited PLA-TPU crystallization due to the improved interfacial interactions, and CNTs hardly facilitated the crystallization of PLA-TPU in the composites. Thermogravimetric analysis revealed the thermal stability improvement of the blends after CNT loading, up to 9°C and 14°C increase at 5 wt.% and 80 wt.% loss, respectively, at 3 phr CNT loading in the PLA/TPU (5:5) blend. The elongation at break (EB) and impact strength (IS) of PLA were improved significantly after forming the blends, especially with ADR incorporation. EB and IS of the PLA/TPU (5:5) blend-based composite increased by up to 70 and 3.4 times, respectively, compared with PLA. Rheological property measurements indicated the formation of a (pseudo)network structure of CNTs in the composites. The inclusion of CNTs improved evidently the anti-dripping performance of the blends in burning tests. The electrical resistivity of the blends decreased by up to seven orders of magnitude at 3 phr CNT loading.

The nearly unlimited supply of cellulose makes this biobased renewable polymer exceptional. Cellulose has low density, nontoxicity, and high biodegradability. Its hierarchical structure is vital for plant life, providing stiffness and facilitating water transportation within the plant. By chemically or physically breaking down cellulose, it is possible to obtain cellulose nanofibers (CNFs), which possess high mechanical strength, reinforcing capabilities, and tunable self-assembly in aqueous media. This unique behavior stems from their shape, size, surface chemistry, and a high degree of crystallinity.
In water suspensions, CNFs have a gel-like structure with excellent stability. When the water is removed, these nanofibers assemble and entangle themselves through hydrogen bonds, forming materials suitable for various applications. CNF films demonstrate remarkable tunability and optical properties, allowing them to be employed as materials for light management. For example, incorporating natural UV-blocking additives into CNF films can enhance the longevity of optoelectronic devices such as solar cells. However, challenges are associated with using CNF films as substrates for optoelectronics. Their affinity for water and tendency to have high surface roughness can negatively impact performance and longevity. Alternatively, by manipulating their surface charge and utilizing their water affinity, CNF films can function effectively as proton exchange membranes, enabling energy production in systems like fuel cells. In conclusion, CNF films are crucial in developing eco-friendly materials for energy harvesting applications, benefiting from their versatility and integrating insights from multiple disciplines.

Materials that respond to the surrounding environment by a shape or colour variation are of great benefit for portable sensors, e.g. to monitor temperature or detect hazardous chemicals, and photonic devices, e.g. dynamic optical filters. For both applications, Liquid Crystalline Networks are suitable candidates thanks to their reversible shape-change and refractive index variation under stimuli, including temperature, light and organic solvents or vapours.
In this communication, we will present the fabrication of micro-structured Liquid Crystalline Networks harnessing the potential of photopolymerization of reactive mesogens. This reaction is compatible with many photolithographic techniques (e.g. Direct Laser Writing, Digital Light Projection lithography) allowing for 3D patterning at the microscale. [1] By exposing the micro-patterns to temperature variations and solvents, we demonstrate a real-time temperature detection and differentiation between organic chemicals by observing the material colour. More precise measurements can be obtained by coupling the responsive polymers with nanometric metal layers, using both a Fabri-Pérot micro-cavities configuration or responsive capacitor one. Regarding the first design, the optical cavities demonstrate large, reversible and linear spectral tuning under temperature variation, working both as tuneable optical filters and temperature sensors. [2] On the other hand, a simple, remote, and continuous monitoring of the environment can be targeted by capacitive measurement, where variation of the dielectric parameters drives remarkable capacitance variation, highlighting by the capability to “sense and act” of smart polymer for applications from micro-robotics to sensing.
Acknowledgment: this project is supported by the Italian Ministry of University and Research (MUR) under the PRIN2022 WATERONIC grant.